Vapor electric device



March 16, 1954 LEwlN 2,671,954

VAPOR ELECTRIC DEVICE Filed June 29, 1951 'Ihlllll;WIIIIIIIIIIIIIIII INVENTOR GEP/MWP LEW/N.

9 ATTORNEY Patented Mar. 16, 1954 VAPOR. ELECTRIC DEVICE Gerhard Lewin, Maplcwood, N. 3., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 29, 1951, Serial No. 234,424

3 Claims.

therefore has not been practical to employ the 1i usual construction of ignitron in mobile units or under conditions involving movement disturbing to the mercury pool, such as occurs with use on water, land or air vehicles. This deficiency may be met in part by employment of a sponge cathode, and in particular by placing a molybdenum insert in an iron sponge, holding mercury, the molybdenum having excellent arcing characteristics without objectionable erosion.

However, this is not a complete solution to the a;

problem, since as ordinarily treated, molybdenum does not readily absorb mercury or under ordinary conditions become wetted thereby.

Accordingly, the primary object of the present invention is to provide a metallic sponge cathode that will absorb and be appropriately wetted by mercury.

A further object of the invention is to provide a sponge cathode which resists poisoning and is readily constructed, mounted and put into operation.

Other objects of the invention will appear to those skilled in the art to which the invention appertains as the description proceeds, both by direct reference thereto and by implication from the context.

Referring to the accompanying drawing, in which like numerals of reference indicate the same parts in both views thereof:

Fig. 1 is a central longitudinal sectional view of an ignitron of arbitrarily selected construction showing my invention embodied therein; and

Fig. 2 is a cross-section on line 11-11 of Fig. 1.

In the specific embodiment of the invention and associated ignitron construction illustrated in the drawing, but without limiting to the details thereof, a cylindrical casing of steel or other sturdy material is shown having a bottom 12 integral therewith and a top header l3 sealed at the upper rim of said casing to provide a closed envelope adapted to be evacuated.

The particular header shown. provides appropriate lead-in seals l4, 15 for electrode leads 16, ll, respectively for an anode l8 and ignitor IS within the casing and supported from said header by said leads. The lead-in seals each include a glass or other insulating sleeve 20 by which the leads are kept electrically distinct from each other and from the casing. The anode I8 is located toward the top of the casing, well above the bottom wall I2, whereas the ignitor I9 is located below the anode, preferably centrally of the casing, and is directed toward and terminates at its bottom in the vicinity of said bottom wall. Said ignitor is shown as relatively slender and tapers downwardly, with its bottom end quite small. Said ignitor may be composed of materials as used for ignitors of the prior art, or may be of such other material or materials adapting it more especially to the present invention.

A sponge cathode, designated generally by numeral 2!, is provided in said container and is of pan-cake shape, and situated upon the bottom wall l2 of the ignitron, preferably fitting the container at its periphery and frictionallyor otherwise held permanently in fixed position. The afore-mentioned lower small end of the isnitor i9 rests upon the upper surface of the sponge cathode 2| in constant contact therewith, and as one means for maintaining such contact without detriment to the lead-in seal I5, the lead-in ii for the ignitor, between the seal and the ignitor, is shown with a transversely extending section 22 which, with the rest of said lead-in, possesses adequate resiliency, supplemented by the weight of the ignitor, to accomplish the purpose. The ignitor projects from its contact on the sponge cathode, at right angles thereto and in a direction longitudinally of the casing. Mercury or other reconstructing liquid cathode material is applied to the sponge cathode 2! to the extent that said sponge will absorb the mercury or the like without any excess remaining on the surface. The sponge cathode 2|, with the absorbed mercury, constitutes the cathode of the ignitron.

In the specific showing of the drawing, the sponge cathode 2! is constructed essentially of two different materials, of which one is used to take advantage of its relatively large interstices between granules for providing generous reservoir capacity, and also to take advantage of its characteristic of afiinity for and absorption of the mercury coming in contact therewith. Selection of the other essential material to constitute the sponge cathode is for purposes of providing an arc-striking surface generously supplied by capillarity through said material with mercury or the like, and to take advantage of resistance to erosion of this other sponge material, during operation. More specifically, the present invention adopts a cathode 2|, by way of example, having a body portion 23 essentially of sintered iron or other material with high absorptive aifinity for the reconstructing cathode fluid, such as the mercury above mentioned, and an arc-striking portion 24 essentially a sintered metal, of which molybdenum, tungsten and tantalum are appropriate examples.

In the specific disclosure arbitrarily selected for illustration in the drawing, the body portion 23 of the sponge cathode is shown relatively flat or thin, of pan-cake shape to fit within the bottom portion of the container fiatwise on the bottom wall thereof and frictionally or otherwise held fixed in that position. The arc-striking portion 24 is shown as a smaller disc than said body portion and embedded therein con- 1*:

centric thereto and according to the present illustration the upper faces of the said body portion and arc-striking portion are in a common plane. The arc-striking portion is thinner than the body portion so that a part of said body portion underlies the arc-striking portion and provides a copious supply of mercury or the like to said arc-striking portion and by capillary action through the arc-striking portion the mercury is ever present at the arc-striking surface. :2

The body portion 23 of compressed sintered granules essentially iron, is employed in conjunction with the centrally disposed arc-striking portion 24 of compressed sintered granules of molybdenum or other material, such as tungsten or tantalum, to take advantage of the inherent characteristics of the iron sponge of more active absorption of mercury coming in contact therewith than would occur with a similarly com pressed sintered body of molybdenum or other metals of the group having the absorptive characteristic.

One difficulty experienced with such metals as molybdenum is that they are very dimcult to wet, especially in the presence or" an ignitor, for

gaseous compounds of the ignitor material and hydrogen are formed during the treatment, which.

react with the molybdenum or the like and rel der it non-wettable.

According to the present invention, the ad.- vantages of both metals can be retained by employing a sponge 24 of molybdenum or the like; The otherwise exposed surfaces, inclusive of the pore surfaces, are coated with iron or corresponding metal, such as nickel. wetted equally well as the iron body 23. the ignitron is completed and use thereof con menced, the iron film will be sputtered away or eroded from the top of the molybdenum or other insert 24, thereby exposing the molybdenum due to the cleaning action of the arc and the molybdenum will continue to be readily wet by the mercury and the arc will form directly on the molybdenum surface. Below the top The coating will be. After surface, the coating of iron or the like remains for the most part on the pore surfaces.

In manufacture, the iron film can be produced by sucking into the spongy material or molybdenum cake, a saturated solution of an easily reduced iron compound, such as ferric oxalate, and heating the sponge in hydrogen. Sucking of the solution into the molybdenum sponge cake is readily accomplished by the capillary action of the sponge material which will avidly absorb. Heating, as specified above, results in reduction of the solution and retention of iron as a film upon and ingredient within the sponge molybdenum cake, and with the sponge in this condition the mercury readily wets it in use.

A sponge of the described character has been made and the correctness of these considerations has been proven by using a mixture of 30% molybdenum and '=O% iron powder, pressing and sintering it as usual. The iron will cover the internal molybdenum surfaces by surface migration. This sponge was treated in a simplified manner which sufiices to wet iron, but not 1 molybdenum. The sponge sucked in the mercury very well, and with use in an ignitron showed very little poisoning by the ignitor which cleaned up quickly and operated smoothly. The sputtering was approximately one-tenth of pure iron.

The principle is, of course, not limited to molybdenum and iron, but may also be applied.

to other combinations of metals, one being resistive to sputtering but difiicult to wet and the other one easily wettable, but subject to erosion, e. g. tungsten and nickel. A tungsten sponge was coated with iron in the following manner:

iron powder was added to the tungsten powder before pressing. After sintering, the sponge was heated for a short time up to the melting point of iron so that the iron flowed over the tungsten particles.

I claim:

1. A sponge cathode comprising pressed and sinter-ed molybdenum, and a film of the iron group on said molybdenum.

2. A sponge cathode comprising a metal resistive to sputtering, and another metal formed as a protective film for the first said metal and more readily wettable by mercury than the first said metal.

3. A sponge cathode comprising pressed and sintered tungsten, and a film of iron on said tungsten.

GERHARD LEWIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,123,861 Tonks Aug. 30, 1938 2,169,032 Slepian Aug. 8, 1939 2,213,386 Smith Oct. 15, 1 40 2,432,513 Depew Dec. 16, 1947 2,617,064 Lewin Nov. 4, 1952 

1. A SPONGE CATHODE COMPRISING PRESSED AND SINTERED MOLYBDENUM, AND A FILM OF THE IRON GROUP ON SAID MOLYDENUM. 